One form of the various types of pointing devices is the conventional (mechanical) mouse, used in conjunction with a cooperating mouse pad. Mechanical mice typically include a rubber-surfaced steel ball that rolls over the mouse pad as the mouse is moved. Interior to the mouse are rollers, or wheels, that contact the ball at its equator and convert its rotation into electrical signals representing orthogonal components of mouse motion. These electrical signals are coupled to a computer, where software responds to the signals to change by a ΔX and a ΔY the displayed position of a pointer (cursor) in accordance with movement of the mouse.
In addition to mechanical types of pointing devices, such as a conventional mechanical mouse, optical pointing devices have also been developed. In one form of an optical pointing device, rather than using a moving mechanical element like a ball, relative movement between an imaging surface, such as a finger or a desktop, and an image sensor within the optical pointing device, is optically sensed and converted into movement information.
Wireless pointing devices have also been developed. Limiting power consumption is important for wireless pointing devices, such as wireless optical mice. Battery life is an important selling feature for wireless mice. One major source of power drain in wireless optical pointing devices is the wireless communications channel. In some wireless optical pointing devices, approximately 50% of the power budget goes to the wireless channel. Most of this power is proportional to the number of bits of motion information that are transmitted via the wireless channel.